Ionizing radiation presents a direct hazard to people; therefore, the measurement of radiation in environmental settings is important. The type of radiation monitor or detector used to measure the radiation depends upon the type of radiation, e.g., beta, alpha or X-ray and the environmental setting, e.g., an environmentally isolated laboratory, an open mine, a waste dump holding potentially hazardous material. The laboratory most likely requires a monitoring system with a continuous display and singular or multiple radiation detectors; the mine requires a moderately sensitive portable area detector; and the waste dump a relatively sensitive, directional detector.
D. A. Waechter et al. describe in an article entitled "New Generation Low Power Radiation Survey Instruments," a standard portable dosimeter (radiation monitor) system. The portable monitor consists of a Geiger-Muller tube (GM tube) with an event counter which records the number of ionizing events. There is a readout display and an audio alarm. The problem with the GM tube is that its response is not linear with the energy of the radiation so its accuracy varies with radiation energy, although it is useful for warning.